1. Field of the Invention
This invention relates to a fabric for plant life and a method for raising plants by using the same. More particularly, the present invention relates to a fabric for plant life which can be efficiently employed in raising plants in, for example, areas with little rainfall (deserts, etc.), areas where considerable labor and a long time are needed for feeding water (golf courses, soccer stadiums, baseball grounds, median strips, etc.) and areas where rainwater can be scarcely retained in the ground (slopes in mountains or residential land, etc.), as well as a method for raising plants by using this fabric for plant life.
2. Description of the Related Art
It has been required to elevate the water retention in soil, relieve the labor for feeding plants with water and reduce the feeding water in, for example, areas where plants can hardly grow because of little rainfall (deserts, etc.), areas where plants can hardly grow because of a lack of soil (rocks, etc.), and areas where considerable labor and a long time are needed for feeding water (golf courses, soccer stadiums, baseball grounds, median strips, etc.).
The conventional techniques aiming at elevating moisture retention include greening sheets consisting of porous sheets (net, woven fabric, etc.) and moisture-absorbent polymers adhered thereto (JP-A-2-16216; the term "JP-A" as used herein means an "Unexamined Japanese Patent Publication"); knit mesh sheets consisting of moisture-absorbent fibers (JP-A-5-247777); and moisture-absorbent woven fabrics in which water-absorbent polymers are adhered to woven structures (JP-A-8-218275). However, these conventional greening sheets and knit mesh sheets generally fail to retain a sufficient volume of moisture needed for raising plants due to insufficient thickness (1 mm or less). When made of thin fibers, such a sheet undergoes compressive deformation under soil pressure and thus loses its voids which are necessary in sustaining moisture retention characteristics and appropriate drainage characteristics and for the growth of plant roots. As a result, there arise withering due to a shortage of water, root rot due to excessive water content, salinization caused by accumulated salts, insufficient growth caused by close rooting, etc.
In the above-mentioned conventional techniques, moreover, no particular discussion is made on the moisture absorbing capacity (moisture absorption), etc. required for the normal growth of plants.
In areas with extremely little rainfall such as deserts, it has been a practice to use desalinated seawater as feeding water. However, a small amount of salt still remains in the desalinated seawater. To raise plants under these circumstances, it is therefore necessary to use a moisture-absorbent material which has a high moisture absorbing capacity. It is also needed that the salt remaining in water is scarcely accumulated in the moisture-absorbent material and, if accumulated, can be easily washed away therefrom. However, these points are never considered in the conventional greening sheets and moisture-absorbent fabrics described above.
In addition to the high moisture absorbing capacity, the prevention of salt accumulation and easiness in washing away salts as described above, it is an important factor of a moisture-absorbent material for greening to have appropriate drainage characteristics, from the viewpoint of preventing root rot due to excessive moisture content. Furthermore, a greening sheet should be provided with voids allowing the healthy growth of plant roots. With respect to these points, however, no sufficient consideration is given in the conventional greening sheets and moisture-absorbent fabrics described above.